Verapamil has been successful in treating supraventricular arrhythmias in two of three patients with hypertrophic cardiomyopathy and in one of three such patients with ventricular arrhythmias. Since arrhythmias are a common source of symptoms and death, and are commonly refractory to standard antiarrhythmic drugs, verapamil theraphy may prove to be an important new approach to the treatment of such patients.